A dynamic recurrent neural network for multiple muscles electromyographic mapping to elevation angles of the lower limb in human locomotion.

This paper describes the use of a dynamic recurrent neural network (DRNN) for simulating lower limb coordination in human locomotion. The method is based on mapping between the electromyographic signals (EMG) from six muscles and the elevation angles of the three main lower limb segments (thigh, shank and foot). The DRNN is a fully connected network of 35 hidden units taking into account the temporal relationships history between EMG and lower limb kinematics. Each EMG signal is sent to all 35 units, which converge to three outputs. Each output neurone provides the kinematics of one lower limb segment. The training is supervised, involving learning rule adaptations of synaptic weights and time constant of each unit. Kinematics of the locomotor movements were recorded and analysed using the opto-electronic ELITE system. Comparative analysis of the learning performance with different types of output (position, velocity and acceleration) showed that for common gait mapping velocity data should be used as output, as it is the best compromise between asymptotic error curve, rapid convergence and avoidance of bifurcation. Reproducibility of the identification process and biological plausibility were high, indicating that the DRNN may be used for understanding functional relationships between multiple EMG and locomotion. The DRNN might also be of benefit for prosthetic control.

Endogenous hypergastrinaemia does not promote growth of colonic mucosa or of a transplanted colon adenocarcinoma in rats.

BACKGROUND/OBJECTIVE: Gastrin is trophic for the mucosa of the acid-producing part of the rat stomach, notably the histamine-producing ECL cells. Gastrin is said to stimulate growth also of colonic mucosa and colon cancer. The purpose of the present study was to examine whether endogenous hypergastrinaemia had trophic effects on normal colonic mucosa and transplanted colon adenocarcinoma in rats. METHODS: Rats were subjected to fundectomy (surgical removal of the acid-producing part of the stomach) or treatments known to induce endogenous hypergastrinaemia. The treatments included refeeding after 48 h of food deprivation or administration of omeprazole (400 micromol/kg/day, orally). Other operations included colostomy and sham operation. A K12-cell line, originally established from a 1,2-dimethylhydrazine-induced colon adenocarcinoma, was used for transplantation. The rates of cell proliferation were determined in the oxyntic and colonic mucosa and in the tumour by measuring the proportion of the cells that accumulated bromodeoxyuridine in their nuclei, i.e. the labelling index (LI). The thickness of the oxyntic mucosa and the activity of histidine decarboxylase (HDC), the histamine-forming enzyme of the ECL cells, were measured. In addition, the thickness of the colonic mucosa and the weight and volume of the tumour were measured. RESULTS: Refeeding or treatment with a single dose of omeprazole in fasted rats raised the serum gastrin concentration and the LI and HDC activity in the oxyntic mucosa; refeeding but not omeprazole raised the LI in the colonic mucosa. In fed rats, hypergastrinaemia induced by fundectomy or treatment with omeprazole (for 10 days) failed to affect either the LI or the thickness of the mucosa of the proximal colon and the excluded distal colon of the colostomized rats. Fundectomy failed to stimulate the growth of the tumour transplants. CONCLUSION: Endogenous hypergastrinaemia did not induce trophic effects on rat colonic mucosa and did not promote growth of a transplanted colon adenocarcinoma in the rat.

Isolation and infusion of donor CD34+ bone marrow cells in cadaver kidney transplantation.

BACKGROUND: Infusion of donor bone marrow cells induces tolerance in allograft models. CD34+ stem cells present in human bone marrow could be endowed with tolerogenic properties. METHODS: CD34+ stem cells were isolated from bone marrow extracted from vertebral bodies of cadaveric donors. Donor CD34+ cells (0.6-3.7 x 10(6)/kg) were infused during surgery in 10 kidney transplant recipients receiving OKT3 as induction therapy. Chimerism was investigated using nested PCR for donor-specific HLA alleles. RESULTS: The infusion of CD34+ stem cells was perfectly tolerated. Five patients remained free of acute rejection at follow-up, 47-325 days post-operatively. The five other patients underwent a single episode of corticosensitive acute rejection. Long-term chimerism was not induced in the seven patients investigated for the persistence of donor DNA. CONCLUSIONS: Infusion of donor CD34+ stem cells in kidney transplantation is safe. The clinical usefulness of the procedure remains to be established.